The present invention concerns a spinning ring made from steel for ring spinning and ring twisting machines with a traveller guide surface, the spinning ring being provided with a hardened structure and with an outer layer into which a non-metal is incorporated by diffusion.
A known spinning ring of the above mentioned type (e.g. as disclosed in U.S. Pat. No. 2,987,871 or U.S. Pat. No. 3,084,501) is subjected, for manufacture after shaping, to a case-hardening operation at 830.degree. C. and subsequently to a sulfuration process in a salt bath at about 565.degree. C. As a result of such processing a soft sulfur-containing surface layer of a thickness ranging from 50.mu. to several tenths of a millimeter is obtained. Subsequently a further case-hardening or induction-hardening process is effected at approximately 855.degree. C. for restoring the hardness lost during the sulfuration process. The outer, hardened layer possesses lubricating properties owing to the incorporated sulfur, which permit a reduction of the running in time required for the traveller. This running-in layer, however, can be worn off completely by the traveller. Thus, the ring not only loses the desirable lubricating properties of the traveller guide surfaces, but also the hardened, surlfur-free steel base is laid bare, in such manner that the known disadvantages of welding of the traveller and the ring again prevail. The ring, after completion of the hardening process, furthermore no longer is of the required shape, e.g. roundness, achieved by the shaping process because the shape is impaired, as is well known, by the hardening processes effected at a temperature above the structure transition temperature. A possible unroundness, possibly corrected in the outer layer, thus again influences the traveller on the hardened steel base. The known spinning rings with hardened structure thus do not possess the desired properties required for the finished operable ring.
Another known spinning ring of hardened steel (Swiss Pat. No. 430,522) is provided with an outer surface layer of soft, unhardened steel, of a depth of about 3 to 50.mu., which is generated by elimination of the carbon owing to the burning out or annealing during the hardening process, and thus to the avoidance of the structure transformation during the hardening process. Notwithstanding the smoothing action of the traveller during the running-in period during which the soft steel is worn off, a ferritic surface is present due to the de-carbonization, which favours the scoring tendency with respect to the traveller. Also with this known spinning ring the disadvantage persists that, as wear of the soft layer progresses, the traveller reaches the hardened steel base, and that e.g. also the correct dimensions of the ring are impaired by the burning out or annealing process which is effected at temperatures above the structure transition temperature. The absence of an alloy component, eliminated during the hardening process, thus does not eliminate the disadvantages of a ring of hardened steel with a non-metal provided in the surface layer.